1. Field of the Invention
The present invention relates to a formed wire for an actuator used in a magnetic disk drive.
2. Description of the Related Art
In recent years, a magnetic disk drive having a high storage capacity of 2 GB or more has become dominant, and in particular a magnetic disk drive having a storage capacity of 1 GB or more per disk and adopting a magnetoresistive head (MR head) as a magnetic head is commercially available in response to the needs for cost reduction and size reduction. In the MR head, a constant sense current is supplied to a magnetoresistive element (MR element) to convert changes in magnitude of a signal field leaking from a recording track of a recording medium into changes in resistance, thereby reproducing information recorded on the recording medium as changes in voltage.
The MR head is mounted on a head slider, and the MR element of the MR head is formed generally by a thin-film process or the like. The MR head further has a coil for writing data to the recording medium. The head slider is mounted by adhesion or the like on a front end portion of a suspension formed of stainless steel. Lead lines for connecting the MR element and the coil to a recording and reproducing circuit in a magnetic disk drive are formed by copper patterns printed on the suspension. A head assembly formed by mounting the head slider on the suspension is mounted on a front end portion of an actuator arm.
A plurality of terminals formed on the head assembly and a plurality of terminals formed on a read/write flexible printed circuit board (read/write FPC) are connected by a twisted wire bundle formed by twisting a plurality of wires. The twisted wire bundle is bonded by adhesion to one side surface of the actuator arm. In bonding the twisted wire bundle to the side surface of the actuator arm, a formed wire prepared by mounting the twisted wire bundle on a polyethylene terephthalate frame (PET frame) is used.
In a conventional formed wire, the plural wires at one end portion of the twisted wire bundle to be connected to the terminals of the head assembly are preliminarily separated from each other and positioned with the spacings of the terminals, so that the plural wires are respectively connected to the terminals of the head assembly at one time by thermal compression bonding. On the other hand, the plural wires at the other end portion of the twisted wire bundle to be connected to the terminals of the read/write FPC remain twisted, so that the twisted wires must be manually untwisted and separate from each other and each separate wire must be set on the corresponding terminal (pad) of the read/write FPC before soldering.
In such a conventional method, wire bonding on the head assembly side is simple because the wires to be connected to the terminals of the head assembly are preliminarily separated and positioned. However, wire bonding on the read/write FPC is troublesome because the following working steps must be carried out.
(1) Separation of the twisted wire bundle from the PET frame PA1 (2) Untwisting of the wires of the twisted wire bundle PA1 (3) Confirmation of positions of the separated wires to the respective terminals and soldering of each separate wire to the corresponding terminal PA1 (4) Adhesive bonding of the twisted wire bundle at its intermediate portion to the actuator arm
Thus, the bonding connection between the wires and the terminals of the read/write FPC is complicated, causing the occurrence of misconnection by an operator. Further, the twisted wire bundle mounted on the PET frame in the conventional formed wire is used for one head, that is, used commonly for an up head and a down head.